Fix assignment with .loc (pydata#8067)

* Add unit test for Variable[...] = DataArray (pydata#7030)

* Check for DataArray instance (pydata#7030)

* Update whats-new.rst (pydata#7030)

* Revert Variable and fix DataArray instead (pydata#7030)

* Add test case for .loc[...] = dataarray (pydata#7030)

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Fix whats-new.rst (pydata#7030)

* Add regression test for Dataset (pydata#7030)

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Maximilian Roos <[email protected]>

doc/whats-new.rst

@@ -60,6 +60,9 @@ Bug fixes
   names were not updated properly internally (:issue:`7405`, :issue:`7588`,
   :pull:`8104`).
   By `Benoît Bovy <https://github.com/benbovy>`_.
+- Fix bug where :py:class:`DataArray` instances on the right-hand side
+  of :py:meth:`DataArray.__setitem__` lose dimension names.
+  (:issue:`7030`, :pull:`8067`) By `Darsh Ranjan <https://github.com/dranjan>`_.
 
 Documentation
 ~~~~~~~~~~~~~

xarray/core/dataarray.py

@@ -856,6 +856,7 @@ def __setitem__(self, key: Any, value: Any) -> None:
             obj = self[key]
             if isinstance(value, DataArray):
                 assert_coordinate_consistent(value, obj.coords.variables)
+                value = value.variable
             # DataArray key -> Variable key
             key = {
                 k: v.variable if isinstance(v, DataArray) else v

xarray/tests/test_dataarray.py

@@ -841,6 +841,27 @@ def get_data():
         )
         da[dict(x=ind)] = value  # should not raise
 
+    def test_setitem_vectorized(self) -> None:
+        # Regression test for GH:7030
+        # Positional indexing
+        v = xr.DataArray(np.r_[:120].reshape(2, 3, 4, 5), dims=["a", "b", "c", "d"])
+        b = xr.DataArray([[0, 0], [1, 0]], dims=["u", "v"])
+        c = xr.DataArray([[0, 1], [2, 3]], dims=["u", "v"])
+        w = xr.DataArray([-1, -2], dims=["u"])
+        index = dict(b=b, c=c)
+        v[index] = w
+        assert (v[index] == w).all()
+
+        # Indexing with coordinates
+        v = xr.DataArray(np.r_[:120].reshape(2, 3, 4, 5), dims=["a", "b", "c", "d"])
+        v.coords["b"] = [2, 4, 6]
+        b = xr.DataArray([[2, 2], [4, 2]], dims=["u", "v"])
+        c = xr.DataArray([[0, 1], [2, 3]], dims=["u", "v"])
+        w = xr.DataArray([-1, -2], dims=["u"])
+        index = dict(b=b, c=c)
+        v.loc[index] = w
+        assert (v.loc[index] == w).all()
+
     def test_contains(self) -> None:
         data_array = DataArray([1, 2])
         assert 1 in data_array

xarray/tests/test_dataset.py

@@ -4202,6 +4202,29 @@ def test_setitem_align_new_indexes(self) -> None:
         )
         assert_identical(ds, expected)
 
+    def test_setitem_vectorized(self) -> None:
+        # Regression test for GH:7030
+        # Positional indexing
+        da = xr.DataArray(np.r_[:120].reshape(2, 3, 4, 5), dims=["a", "b", "c", "d"])
+        ds = xr.Dataset({"da": da})
+        b = xr.DataArray([[0, 0], [1, 0]], dims=["u", "v"])
+        c = xr.DataArray([[0, 1], [2, 3]], dims=["u", "v"])
+        w = xr.DataArray([-1, -2], dims=["u"])
+        index = dict(b=b, c=c)
+        ds[index] = xr.Dataset({"da": w})
+        assert (ds[index]["da"] == w).all()
+
+        # Indexing with coordinates
+        da = xr.DataArray(np.r_[:120].reshape(2, 3, 4, 5), dims=["a", "b", "c", "d"])
+        ds = xr.Dataset({"da": da})
+        ds.coords["b"] = [2, 4, 6]
+        b = xr.DataArray([[2, 2], [4, 2]], dims=["u", "v"])
+        c = xr.DataArray([[0, 1], [2, 3]], dims=["u", "v"])
+        w = xr.DataArray([-1, -2], dims=["u"])
+        index = dict(b=b, c=c)
+        ds.loc[index] = xr.Dataset({"da": w}, coords={"b": ds.coords["b"]})
+        assert (ds.loc[index]["da"] == w).all()
+
     @pytest.mark.parametrize("dtype", [str, bytes])
     def test_setitem_str_dtype(self, dtype) -> None:
         ds = xr.Dataset(coords={"x": np.array(["x", "y"], dtype=dtype)})